The present invention relates to the field of aeronautical equipment racks and Line Replaceable Unit trays that retain Line Replaceable Units (LRUs), and specifically to techniques for addressing problems associated with empty Line Replaceable Unit trays.
Aircraft and other vehicles and systems commonly include Line Replaceable Units disposed on LRU trays in equipment racks within their fuselage. LRUs often include electronic equipment, computers, radio, avionics, flight systems, entertainment systems and other auxiliary electronic equipment.
LRU trays support the LRUs in the equipment rack and provide connectors between the LRUs and the electrical systems in the aircraft. A LRU tray may include a bracket to support the LRU, hold-down fastening elements to secure LRUs to the LRU trays, connectors to connect with the LRUs, and airflow openings to allow airflow through the LRU tray to the LRU.
LRU trays and the equipment racks that house the trays enable LRUs to be easily removed and replaced. To remove and replace an LRU, the hold-down fastening elements are released and the LRU is removed from the LRU tray which disconnects the connectors on the LRU from the electrical system for the aircraft. A replacement LRU is slid onto the LRU tray such that the connectors on the back of the LRU engage the connectors on the back of the tray, and the hold-down fastening elements are tightened to secure the LRU to the tray.
Some LRU trays in an equipment rack may be empty. There is typically no requirement of an equipment rack that all LRU trays be filled and there are advantages to having empty trays that can be filled if a need arises for another LRU.
If a LRU tray is left empty, the electrical connectors at the back of the empty LRU tray may be covered. The connectors may be covered with caps or other devices that shield the connectors. The caps or other covering devices may not be secured to the connectors and thus may not properly seal the connectors from water and debris.
An empty LRU tray may have unsecured hold-down fastening elements. These fastening elements typically are threaded and turn to engage the LRU. If there is no LRU in a tray, the hold-down fastening elements are not secured and thus prone to vibrate during operation of the aircraft. Vibration can create unwanted noise and wear the fastening elements.
Air flows through the equipment racks to provide cooling air for the electronic components of the LRUs. The airflow through the equipment rack and the LRUs is affected by empty trays. An empty tray may offer less resistance to air flow than a tray supporting an LRU.